Effects of crossbreeding and certain environmental factors on multiple births, wool production and growth in sheep

Abstract

Multiple birth percentage and wool production were studied on 338 ewes (907 lambing and 873 shearing records) representing two purebreds, Oxford (O) and Suffolk (S), and four crossbreds, O x S, S x O, Cheviot (C) x O and C x S mated to purebred and crossbred rams during 9 years. Oxford ewes had 24-32% (P<0-01) fewer multiple births than ewes of the other groups, while little difference between S and the crossbreds was observed. The heterosis of the 05 and SO groups was 14-6 + 4-1%. Multiple births tended to increase 0-8% for each kg increase in body weight of the dam (r = 0-13). The repeatability estimate for multiple births was 0-24. Fleece weight was significantly affected by age and by breed group, with OS and SO crosses producing 17% more wool than their parental breeds. The repeatability of fleece weight was estimated at 0-52 + 0-15. Fleece weight was significantly correlated with multiple birth percentage (0-09) and body weight (0-32). Suffolk ewes averaged 9-5 kg heavier than O ewes throughout their reproductive life. The two reciprocal crosses were heavier than both parental breeds. Suffolk ewes reached their maximum body weight at 4 years of age while Oxfords continued to gain weight up to 6 years.

Maternal performance of oxford and suffolk breeds, of sheep, and their crosses

“…For example, in the present study, the performance of the particular sample of the O breed involved was markedly different from the S in terms of prolificacy and body weights (Fahmy and Bernard, 1973), hence the higher estimates of heterosis. The O and S are both large breeds of mediumwool type, and are similar in many other characteristics.…”

“…Their estimate of 0-157 for the heterosis in weight of lambs weaned per ewe lambing is close to our present estimate of 018. Using the present data, Fahmy and Bernard (1973) reported a heterosis of 0146 for multiple birth, a character very much associated with litter size at birth. Using the present data, Fahmy and Bernard (1973) reported a heterosis of 0146 for multiple birth, a character very much associated with litter size at birth.…”

“…The popularity among commercial producers, in view P " " *^ merit of any particular cross has to be of the generally superior performance of the established by experimentation. Despite the relatively Bernard, 1973), were reported, abundant information on the effect of crossbreeding as such (reviewed by Rae (1952), , . In sheep breeding, the better ( Q breeds are presented, and compared with the performance of the crossbred ewes over the Performance of the pure O and S breeds.…”

“…In sheep breeding, the better ( Q breeds are presented, and compared with the performance of the crossbred ewes over the Performance of the pure O and S breeds. The origin and management of the flock have been reported in detail by Holtmann and Bernard (1969) and Fahmy and Bernard (1973). Despite the relatively Bernard, 1973), were reported, abundant information on the effect of crossbreeding as such (reviewed by Rae (1952), , .…”

“…The data were analyzed using a sequential procedure of fitting constants (Fahmy and Bernard, 1973). The following mixed model was assumed: where bs refers to breed of sire; s to sires within breed of sire; bd to breed of dam; d to dams within breed of dam; (bs x bd) to the interaction breed of sire x breed of dam; ad to age of dam; as to age of sire; and r to years.…”